Irish homes could be forced into lockdown in the event of a major meltdown at a nuclear power plant in the UK, experts have warned.

The Radiological Protection Institute of Ireland (RPII) predicted people could be forced to stay indoors for days were an accident to occur at any of the eight plants dotted along the west coast of Britain.

Chief executive Dr Ann McGarry said while a potential accident would result in "no observable health impacts", the socio-economic consequences would be much worse.

"People might be advised to stay in doors for a period of time. It could be from hours to possibly a day or two," Dr McGarry said.

"For most of the accident scenarios that we looked at, some food controls would be necessary.

"The amount of radioactivity reaching Ireland wouldn't be enough to directly impact the health of people, but if food contaminated wasn't taken off shelves and people ate it, it would have some impact."

Dr McGarry said radiation from a leak, spill or explosion would travel from the UK to Ireland by sea and air.

But what might initially be large amounts would be diluted in water or fail to travel the distance across the Irish Sea to be high enough to pose a serious risk.

The seven existing nuclear power plants in the UK are to be shut down by 2023.

It is proposed the plants will be replaced and eight new sites have been identified for construction.

Dr McGarry, during a grilling by members of the Oireachtas environment committee, played down any potential risks to Ireland that would result from their build.

She said one accident scenario had been identified in which cancer results could increase.

"From day-to-day operations, we do not believe there is a health risk, but we did look at one accident scenario where there would be an increase in cancer rates if things went badly wrong," Dr McGarry said.

Responding to concerns about old tanks used at the Sellafield power station in Cumbria, the RPII chief insisted they posed no real danger to Ireland.

She likened the tanks to swimming pools above ground, saying if there were an explosion similar to that at Chernobyl in the 1980s, there would not be the same level of power to lift the radioactivity into the air for it to travel to Ireland.

The only way this could be achieved, she said, would be with a meteorite.

"If a meteorite were to hit a tank and release radioactivity into the air, then in that sort of scenario we could have some impact in Ireland."